[clang] [llvm] Add f8E4M3 IEEE 754 type to llvm (PR #97179)
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Sat Jun 29 13:10:08 PDT 2024
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-llvm-support
Author: Alexander Pivovarov (apivovarov)
<details>
<summary>Changes</summary>
This PR adds `f8E4M3` type to llvm.
`f8E4M3` type follows IEEE 754 convention
```c
f8E4M3 (IEEE 754)
- Exponent: 4
- Mantissa: 3
- Exponent bias: 7
- Follows IEEE 754 conventions for representation of special values
- Has Positive and Negative zero
- Has Positive and Negative infinity
- Has NaNs
Additional details:
- Max exp (unbiased): 7
- Min exp (unbiased): -6
- Infinities (+/-): S.1111.000
- Zeros (+/-): S.0000.000
- NaNs: S.1111.{001, 010, 011, 100, 101, 110, 111}
- Max normal number: S.1110.111 = +/-240
- Min normal number: S.0001.000 = +/-2^(-6)
- Max subnormal number: S.0000.111 = +/-2^(-6) x 0.875 = +/-2^(-9) x 7
- Min subnormal number: S.0000.001 = +/-2^(-6) x 0.125 = +/-2^(-9)
```
Related PRs:
- [PR-97118](https://github.com/llvm/llvm-project/pull/97118) Add f8E4M3 IEEE 754 type to mlir
---
Full diff: https://github.com/llvm/llvm-project/pull/97179.diff
5 Files Affected:
- (modified) clang/include/clang/AST/Stmt.h (+3-3)
- (modified) clang/lib/AST/MicrosoftMangle.cpp (+1)
- (modified) llvm/include/llvm/ADT/APFloat.h (+6)
- (modified) llvm/lib/Support/APFloat.cpp (+20)
- (modified) llvm/unittests/ADT/APFloatTest.cpp (+38)
``````````diff
diff --git a/clang/include/clang/AST/Stmt.h b/clang/include/clang/AST/Stmt.h
index 9cd7a364cd3f1..4edb04502f83e 100644
--- a/clang/include/clang/AST/Stmt.h
+++ b/clang/include/clang/AST/Stmt.h
@@ -460,10 +460,10 @@ class alignas(void *) Stmt {
unsigned : NumExprBits;
static_assert(
- llvm::APFloat::S_MaxSemantics < 16,
- "Too many Semantics enum values to fit in bitfield of size 4");
+ llvm::APFloat::S_MaxSemantics < 32,
+ "Too many Semantics enum values to fit in bitfield of size 5");
LLVM_PREFERRED_TYPE(llvm::APFloat::Semantics)
- unsigned Semantics : 4; // Provides semantics for APFloat construction
+ unsigned Semantics : 5; // Provides semantics for APFloat construction
LLVM_PREFERRED_TYPE(bool)
unsigned IsExact : 1;
};
diff --git a/clang/lib/AST/MicrosoftMangle.cpp b/clang/lib/AST/MicrosoftMangle.cpp
index 7f1e9ab02ec26..a2e270df276cb 100644
--- a/clang/lib/AST/MicrosoftMangle.cpp
+++ b/clang/lib/AST/MicrosoftMangle.cpp
@@ -946,6 +946,7 @@ void MicrosoftCXXNameMangler::mangleFloat(llvm::APFloat Number) {
case APFloat::S_IEEEquad: Out << 'Y'; break;
case APFloat::S_PPCDoubleDouble: Out << 'Z'; break;
case APFloat::S_Float8E5M2:
+ case APFloat::S_Float8E4M3:
case APFloat::S_Float8E4M3FN:
case APFloat::S_Float8E5M2FNUZ:
case APFloat::S_Float8E4M3FNUZ:
diff --git a/llvm/include/llvm/ADT/APFloat.h b/llvm/include/llvm/ADT/APFloat.h
index db2fa480655c6..bff8e6490d1de 100644
--- a/llvm/include/llvm/ADT/APFloat.h
+++ b/llvm/include/llvm/ADT/APFloat.h
@@ -166,6 +166,9 @@ struct APFloatBase {
// This format's exponent bias is 16, instead of the 15 (2 ** (5 - 1) - 1)
// that IEEE precedent would imply.
S_Float8E5M2FNUZ,
+ // 8-bit floating point number following IEEE-754 conventions with bit
+ // layout S1E4M3.
+ S_Float8E4M3,
// 8-bit floating point number mostly following IEEE-754 conventions with
// bit layout S1E4M3 as described in https://arxiv.org/abs/2209.05433.
// Unlike IEEE-754 types, there are no infinity values, and NaN is
@@ -217,6 +220,7 @@ struct APFloatBase {
static const fltSemantics &PPCDoubleDouble() LLVM_READNONE;
static const fltSemantics &Float8E5M2() LLVM_READNONE;
static const fltSemantics &Float8E5M2FNUZ() LLVM_READNONE;
+ static const fltSemantics &Float8E4M3() LLVM_READNONE;
static const fltSemantics &Float8E4M3FN() LLVM_READNONE;
static const fltSemantics &Float8E4M3FNUZ() LLVM_READNONE;
static const fltSemantics &Float8E4M3B11FNUZ() LLVM_READNONE;
@@ -638,6 +642,7 @@ class IEEEFloat final : public APFloatBase {
APInt convertPPCDoubleDoubleAPFloatToAPInt() const;
APInt convertFloat8E5M2APFloatToAPInt() const;
APInt convertFloat8E5M2FNUZAPFloatToAPInt() const;
+ APInt convertFloat8E4M3APFloatToAPInt() const;
APInt convertFloat8E4M3FNAPFloatToAPInt() const;
APInt convertFloat8E4M3FNUZAPFloatToAPInt() const;
APInt convertFloat8E4M3B11FNUZAPFloatToAPInt() const;
@@ -656,6 +661,7 @@ class IEEEFloat final : public APFloatBase {
void initFromPPCDoubleDoubleAPInt(const APInt &api);
void initFromFloat8E5M2APInt(const APInt &api);
void initFromFloat8E5M2FNUZAPInt(const APInt &api);
+ void initFromFloat8E4M3APInt(const APInt &api);
void initFromFloat8E4M3FNAPInt(const APInt &api);
void initFromFloat8E4M3FNUZAPInt(const APInt &api);
void initFromFloat8E4M3B11FNUZAPInt(const APInt &api);
diff --git a/llvm/lib/Support/APFloat.cpp b/llvm/lib/Support/APFloat.cpp
index 3017a9b976658..79e0094b243b2 100644
--- a/llvm/lib/Support/APFloat.cpp
+++ b/llvm/lib/Support/APFloat.cpp
@@ -136,6 +136,7 @@ static constexpr fltSemantics semIEEEquad = {16383, -16382, 113, 128};
static constexpr fltSemantics semFloat8E5M2 = {15, -14, 3, 8};
static constexpr fltSemantics semFloat8E5M2FNUZ = {
15, -15, 3, 8, fltNonfiniteBehavior::NanOnly, fltNanEncoding::NegativeZero};
+static constexpr fltSemantics semFloat8E4M3 = {7, -6, 4, 8};
static constexpr fltSemantics semFloat8E4M3FN = {
8, -6, 4, 8, fltNonfiniteBehavior::NanOnly, fltNanEncoding::AllOnes};
static constexpr fltSemantics semFloat8E4M3FNUZ = {
@@ -208,6 +209,8 @@ const llvm::fltSemantics &APFloatBase::EnumToSemantics(Semantics S) {
return Float8E5M2();
case S_Float8E5M2FNUZ:
return Float8E5M2FNUZ();
+ case S_Float8E4M3:
+ return Float8E4M3();
case S_Float8E4M3FN:
return Float8E4M3FN();
case S_Float8E4M3FNUZ:
@@ -246,6 +249,8 @@ APFloatBase::SemanticsToEnum(const llvm::fltSemantics &Sem) {
return S_Float8E5M2;
else if (&Sem == &llvm::APFloat::Float8E5M2FNUZ())
return S_Float8E5M2FNUZ;
+ else if (&Sem == &llvm::APFloat::Float8E4M3())
+ return S_Float8E4M3;
else if (&Sem == &llvm::APFloat::Float8E4M3FN())
return S_Float8E4M3FN;
else if (&Sem == &llvm::APFloat::Float8E4M3FNUZ())
@@ -276,6 +281,7 @@ const fltSemantics &APFloatBase::PPCDoubleDouble() {
}
const fltSemantics &APFloatBase::Float8E5M2() { return semFloat8E5M2; }
const fltSemantics &APFloatBase::Float8E5M2FNUZ() { return semFloat8E5M2FNUZ; }
+const fltSemantics &APFloatBase::Float8E4M3() { return semFloat8E4M3; }
const fltSemantics &APFloatBase::Float8E4M3FN() { return semFloat8E4M3FN; }
const fltSemantics &APFloatBase::Float8E4M3FNUZ() { return semFloat8E4M3FNUZ; }
const fltSemantics &APFloatBase::Float8E4M3B11FNUZ() {
@@ -3617,6 +3623,11 @@ APInt IEEEFloat::convertFloat8E5M2FNUZAPFloatToAPInt() const {
return convertIEEEFloatToAPInt<semFloat8E5M2FNUZ>();
}
+APInt IEEEFloat::convertFloat8E4M3APFloatToAPInt() const {
+ assert(partCount() == 1);
+ return convertIEEEFloatToAPInt<semFloat8E4M3>();
+}
+
APInt IEEEFloat::convertFloat8E4M3FNAPFloatToAPInt() const {
assert(partCount() == 1);
return convertIEEEFloatToAPInt<semFloat8E4M3FN>();
@@ -3681,6 +3692,9 @@ APInt IEEEFloat::bitcastToAPInt() const {
if (semantics == (const llvm::fltSemantics *)&semFloat8E5M2FNUZ)
return convertFloat8E5M2FNUZAPFloatToAPInt();
+ if (semantics == (const llvm::fltSemantics *)&semFloat8E4M3)
+ return convertFloat8E4M3APFloatToAPInt();
+
if (semantics == (const llvm::fltSemantics *)&semFloat8E4M3FN)
return convertFloat8E4M3FNAPFloatToAPInt();
@@ -3902,6 +3916,10 @@ void IEEEFloat::initFromFloat8E5M2FNUZAPInt(const APInt &api) {
initFromIEEEAPInt<semFloat8E5M2FNUZ>(api);
}
+void IEEEFloat::initFromFloat8E4M3APInt(const APInt &api) {
+ initFromIEEEAPInt<semFloat8E4M3>(api);
+}
+
void IEEEFloat::initFromFloat8E4M3FNAPInt(const APInt &api) {
initFromIEEEAPInt<semFloat8E4M3FN>(api);
}
@@ -3951,6 +3969,8 @@ void IEEEFloat::initFromAPInt(const fltSemantics *Sem, const APInt &api) {
return initFromFloat8E5M2APInt(api);
if (Sem == &semFloat8E5M2FNUZ)
return initFromFloat8E5M2FNUZAPInt(api);
+ if (Sem == &semFloat8E4M3)
+ return initFromFloat8E4M3APInt(api);
if (Sem == &semFloat8E4M3FN)
return initFromFloat8E4M3FNAPInt(api);
if (Sem == &semFloat8E4M3FNUZ)
diff --git a/llvm/unittests/ADT/APFloatTest.cpp b/llvm/unittests/ADT/APFloatTest.cpp
index 86a25f4394e19..132e95bd45f77 100644
--- a/llvm/unittests/ADT/APFloatTest.cpp
+++ b/llvm/unittests/ADT/APFloatTest.cpp
@@ -2133,6 +2133,8 @@ TEST(APFloatTest, getZero) {
{&APFloat::Float8E5M2(), true, true, {0x80ULL, 0}, 1},
{&APFloat::Float8E5M2FNUZ(), false, false, {0, 0}, 1},
{&APFloat::Float8E5M2FNUZ(), true, false, {0, 0}, 1},
+ {&APFloat::Float8E4M3(), false, true, {0, 0}, 1},
+ {&APFloat::Float8E4M3(), true, true, {0x80ULL, 0}, 1},
{&APFloat::Float8E4M3FN(), false, true, {0, 0}, 1},
{&APFloat::Float8E4M3FN(), true, true, {0x80ULL, 0}, 1},
{&APFloat::Float8E4M3FNUZ(), false, false, {0, 0}, 1},
@@ -6846,6 +6848,42 @@ TEST(APFloatTest, Float8E5M2ToFloat) {
EXPECT_TRUE(std::isnan(QNaN.convertToFloat()));
}
+TEST(APFloatTest, Float8E4M3ToFloat) {
+ APFloat PosZero = APFloat::getZero(APFloat::Float8E4M3());
+ APFloat PosZeroToFloat(PosZero.convertToFloat());
+ EXPECT_TRUE(PosZeroToFloat.isPosZero());
+ APFloat NegZero = APFloat::getZero(APFloat::Float8E4M3(), true);
+ APFloat NegZeroToFloat(NegZero.convertToFloat());
+ EXPECT_TRUE(NegZeroToFloat.isNegZero());
+
+ APFloat One(APFloat::Float8E4M3(), "1.0");
+ EXPECT_EQ(1.0F, One.convertToFloat());
+ APFloat Two(APFloat::Float8E4M3(), "2.0");
+ EXPECT_EQ(2.0F, Two.convertToFloat());
+
+ APFloat PosLargest = APFloat::getLargest(APFloat::Float8E4M3(), false);
+ EXPECT_EQ(240.0F, PosLargest.convertToFloat());
+ APFloat NegLargest = APFloat::getLargest(APFloat::Float8E4M3(), true);
+ EXPECT_EQ(-240.0F, NegLargest.convertToFloat());
+ APFloat PosSmallest =
+ APFloat::getSmallestNormalized(APFloat::Float8E4M3(), false);
+ EXPECT_EQ(0x1.p-6, PosSmallest.convertToFloat());
+ APFloat NegSmallest =
+ APFloat::getSmallestNormalized(APFloat::Float8E4M3(), true);
+ EXPECT_EQ(-0x1.p-6, NegSmallest.convertToFloat());
+
+ APFloat SmallestDenorm = APFloat::getSmallest(APFloat::Float8E4M3(), false);
+ EXPECT_TRUE(SmallestDenorm.isDenormal());
+ EXPECT_EQ(0x1.p-9, SmallestDenorm.convertToFloat());
+
+ APFloat PosInf = APFloat::getInf(APFloat::Float8E4M3());
+ EXPECT_EQ(std::numeric_limits<float>::infinity(), PosInf.convertToFloat());
+ APFloat NegInf = APFloat::getInf(APFloat::Float8E4M3(), true);
+ EXPECT_EQ(-std::numeric_limits<float>::infinity(), NegInf.convertToFloat());
+ APFloat QNaN = APFloat::getQNaN(APFloat::Float8E4M3());
+ EXPECT_TRUE(std::isnan(QNaN.convertToFloat()));
+}
+
TEST(APFloatTest, Float8E4M3FNToFloat) {
APFloat PosZero = APFloat::getZero(APFloat::Float8E4M3FN());
APFloat PosZeroToFloat(PosZero.convertToFloat());
``````````
</details>
https://github.com/llvm/llvm-project/pull/97179
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